1. Field of the Invention
The present invention relates generally to magnetic tape systems, and more specifically to dataset migration and backup for tape systems.
2. Background of the Invention
Many tape systems use dataset migration/backup. Host software for backup uses a channel command that instructs the tape drive to write the dataset to tape before any further data is sent from the host. Although this type of hand shaking for data transfer produces extremely slow transfers, many systems still use such software.
Product road maps for tape systems generally show an increase in host transfer rates. With these requirements and changes, high-density recording and fast tape speed are needed. As the full operating speed for tape drives increases, the time needed to accelerate and decelerate increases, as a way of keeping product costs down. The total time needed to decelerate, reposition and ramp up to full speed is known as the repositioning time. Though it is possible to reduce these times, such methods would also add considerable costs to the drives. Data cannot continue to be written until the repositioning of the tape is complete and the drive is back up to full operating speed. Full operating speed is a predefined tape speed at which data is written onto the tape. A data buffer usually masks this latent time so that the host never sees any performance degradation.
When the customer up-grades to a newer generation tape drive, certain expectations are present for the performance for which they are paying. This performance may be, for example, only capacity and throughput. When using software that uses the “Tape write immediate” command, throughput is actually decreased due to the increase in reposition time.
Therefore, it would be desirable to have a method for reducing the effects of repositioning times on total performance throughput.